Lubricated thread



Patented Nov. 27, 1 951 UNITED STATES PATENT OFFICE LUBRICATED THREAD Arthur Cresswel l, Stamford, and Edwin P. Johnstone, J r., Glenbrook, Conn., assignors to American Cyanamid Company, New York, N. Y., a

corporation of Maine No Drawing. Application April 19, 1948, Serial No. 663,600

8 Claims. (Cl. 128-3355) oleic acid, linoleic acid, myristic acid and the like.

Specific examples of such lubricating agents are olive oil and cottonseed oil. In the preparation of collagen filaments for suture use, difliculty is experienced in using such softening agents because 01. irritation of the tissue. On the other hand, a lubricant must be employed or the multifilament collagen strand emerging from the spinnerette will coalesce to a unitary strand having brittle, straw-like characteristics which is unworkable for suture purposes. In the case of multi-filament collagen threads a lubricant not only serves to prevent such coalescence but, further, it permits slippage between the filaments, thus enhancing the flexibility of the multi-filament thread and permitting the preparation of twisted and braided threads.

An object of the present invention is to provide a lubricated multi-filament collagen thread which may be used for suture purposes without irritation. of the tissue.

A further object of the present invention is to provide a lubricated multi-fllament collagen thread of sufllcient flexibility that a highly twisted multi-filament thread may be prepared therefrom.

A still further object is to provide a lubricated multi-filament collagen thread of suillcient flexibility that twisted threads prepared therefrom may be used in the preparation of braided suture threads.

These and other objects are accomplished by the process of the present invention.

It has been discovered that a phosphatide such as lecithin, cephalin, sphingomyelin and the like may be employed in the lubrication of collagen filaments, threads and the like provided that it is applied at the time of coagulation or regeneration of the collagen to form the collagen filament or strand. Such application at the time of coagulation is effected by emulsifying the phosphatide in the spinning bath.

While it is not known for certainty just what the mechanism is by which the lubricating action occurs, apparently effective lubrication is only obtained if the lubricant is incorporated at the time of the coagulation which results in the thread or filament formation. Attempts have been made to effect lubrication by adding a lubricant to the liquified collagen which is extruded into the spinning bath as well as by applying the lubricant to the finished thread but such attempts have proved unsuccessful.

The preferred agent for the emulsiflcation of I the phosphatides in the spinning bath is N-octadecyl tetrasodium N(1,2-dicarboxy-ethyl) sulfosuccinamate which has the following formula:

om-000m Such succinamate is particularly suitable since the large concentration of salts present in the spinning bath does not appear to detract from its efilciency in emulsifying the lubricant therein. The succinamate may, be employed in a range of 1-25 g. per liter of spinning solution, preferably at a concentration of 10 g. per liter. Obviously, other succinamates may be used successfully, particularly those in which the octadecyl radical of the above formula is replaced by other long aliphatic radicals, as, for example, dodecyl, tetradecyl, heptadecyl, and the like.

The lubricating agent is employed in a coagulating bath of the type composed of inorganic salt coagulants and may not be used in coagulating or spinning baths which rely for their effectiveness upon the presence of organic materials such as ethyl alcohol, acetone, ethylene glycol mono ethyl ether, diacetone alcohol and the like in which the softening agent would have a greater tendency to dissolve. Examples of inorganic salts commonly used in spinning baths employed in the preparation of protein filaments and threads are Na2SO4, A12(SO4) 3, (NH4)2SO4 and the like, and these are employed in the highest feasible concentration, (NH4)2SO4 being preferred because of its greater solubility (about 42%).

The phosphatides are generally employed in a concentration of about 5-20 g. per liter with respect to the spinning bath, preferably being employed in an amount of 10 g. per liter. The temperature employed in spinning collagen filaments and threads is maintained low, preferably of the order of 20 C.

awaeve The advantages resulting from the present invention reside in the provision of lubricated collagen filaments from which multi-filament thread may be prepared without danger of coalescence and that such multi-filament thread may be employed as a suture thread without the problem of irritation of tissue. In addition, the successful lubrication of the collagen filaments also enhances the flexibility of the multi-filament threads prepared therefrom. to such a degre that they may be used in preparing a twisted mu ti-filament thread, said twisting greatly enhancing the physical properties of the thread, particularly with respect to the elimination of fraying and the increase in tensile strength. Moreover, the degree offiexibility imparted permits the use of the twisted multi-filament threads in the preparation "of braided or ply twisted threads of still greater tensile strength and of much greater preferability as a suture material. Still further, the phosphatide lubricant is more strongly adherent to the collagen filaments so that the lubricant is not removed during subsequent liquid treatment to the extent that fatty oils are removed, possibly due to an amnity between the carboxyl groups of the collagen and the basic nitrogen of the phosphatides. In addition, the above described succinamate emulsitying agent which is preferred for emulsifying the lubricant in the spinning bath, while not present to any very appreciable extent on the finished lubricated filament is nevertheless rendered still less a source of concern by its being nonirritating to tissue.

A detailed example of the preferred embodiment of the present invention follows: A collagen solution is prepared by treating the cleaned corium of hide or skin material with a solution of organic acid at a pH in the range of 2-4 for about 16-24 hours at -30 C. Following the swelling, the material is mechanically subdivided in various types of apparatus ranging in type from a meat grinder to a colloid mill, frequent filtration being employed after the various operations. Final solution is obtained by adjusting the pH to 2-4 by the addition of organic acid. Such a solution is substantially free from fibers or fibrous material and may be extruded through small orifices and formed into very fine filaments of exceptional uniformity and purity to render them especially adaptable for use as sutures. An

amount of lecithin suificient to give a concentra tion of 10 g. per liter is emulsified in an ammonium sulfate bath containing at least 35% ammonium sulfate using 10 g. per liter of the above succinamate. This spinning bath is employed in the coagulation of collagen filaments which result from the extrusion ofa collagen solution containing from 5-15% collagen through a spinnerette having orifices of the order of 120 microns. The coagulated, lubricated collagen filaments are thereafter spooled and subjected to suitable processing steps such as stretching, hardening and final drying whereafter they may be twisted to form a multi-filament twisted thread which may be used as such or if desired may be used in the preparation of the stronger, preferred braided suture.

In addition to the aforementioned twisted multi-filament threads there are, of course, the twisted plied strands resulting from the twisting 4 together of two or more twisted multi-filament threads.

' twist is employed in preparing such twisted plied strands, as, for example, where the filaments have been twisted counter-clockwise to form a midti-fil inent thread, two or more of the latter are then twisted clockwise to form a twisted plied strand.

The collagen filaments to which the process of the present invention may be applied may result from the regeneration of any extrudable collagenous material which includes swollen and pulped collagen of a pasty consistency as well as the collagen solution employed in the preferred embodiment so long as the diameter of the resulting filament is not so excessive as to exclude its use in the preparation of a multi-filament thread of conventional size and filament number. While for suture purposes the preferred filament diameter is of the order of 10 microns and such filaments are employed in, for example,

a 40 filament thread, a diameter as high as about microns may be lubricated in accordance with the process of the present invention and used in the preparation of twisted multi-filament threads, which in turn may be used in the preparation of braided threads or strands.

While the invention has been described with reference to a particular embodiment, it is nevertheless to be construed broadly and limited solely by the scope of the appended claims.

What is claimed is:

1. A non-irritating collagen suture carrying a lubricating film of a phosphatide.

2. The product of claim 1 in which the phosphatide is a lecithin.

3. A multi-filament collagen suture in which the filaments carry a lubricating film of a phos-' phatide, which suture is non-irritating to animal tissue. a

4. The product of claim 3 in which the phosphatide is lecithin.

5. A braided collagen suture prepared from multi-filament threads composed of filaments carrying a lubricating film of a phosphatide, which suture is non-irritating to human tissue.

6. The product of claim 5 in which the phosphatide is lecithin.

7. A twisted and plied collagen suture prepared from multi-filament threads composed of filaments carrying a lubricating film of a phosphatide, which suture is non-irritating to human tissue.

8. The product of claim 7 in which the phos phatide is lecithin.

ARTHUR CRESSWELL. EDWIN P. JOHNSTONE, JR.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,856,713 Lecompte May 3, 1932 1,872,913 Dreyfus et a1. Aug. 23, 1932 1,999,641 Sharp Apr. 30, 1935 2,039,263 Schulte Apr. 28, 1936 2,163,588 Cronish June 27, 1939 2,195,930 Koch Apr. 2, 1949 2,309,113 Huppert Jan. 26, 1943 Frequently where desired a reverse. 

1. A NON-IRRITATING COLLAGEN SUTURE CARRYING A LUBRICATING FILM OF A PHOSPHATIDE. 